Switchable roller finger followers are known. See, for example, U.S. Pat. No. 7,174,869. Such finger followers have an outer lever as a secondary lever pivotably mounted outside an inner lever acting as a primary lever and a roller rotatably mounted on a transverse axle in a slot in the inner lever. The top surface of the outer lever acts as a contact surface for a high lift cam and the top surface of the roller acts as a contact surface for a low lift cam. A coupling element is mounted at one end of the finger follower and oil from an oil source is used to activate the coupling element. When the coupling element is activated, it locks the outer lever to the inner or primary lever and requires the finger follower to follow the high lift cam and transfer the lift to the valve stem of an associated intake or exhaust valve. When the coupling element is deactivated, the outer or secondary lever is free to pivot relative to the inner or primary lever and, under the aid of a spring, the outer lever pivots freely in conjunction with the high lift cam while the motion of the low lift cam is transferred by the inner lever to the valve stem. This movement by the outer lever is conventionally referred to as the lost motion stroke.
Conventionally, the outer lever is a unitary structure such that the coupling element need only operate on one part of the outer lever. Typically, the coupling device operates on a yoke portion of the outer layer, the yoke portion being transverse to the longitudinal axis of the finger follower. Conventionally, the roller axle is staked to the inner lever to maintain its lateral position relative to the inner lever. U.S. Pat. No. 7,909,007 discloses a roller finger follower of this type. This provides a lost motion spring to maintain contact between the cam follower and the cam.
U.S. Pat. No. 8,251,032 discloses a prior switchable roller finger follower of the inventor in which two locking pins of the coupling device are extended outwardly to a locked position under each of outer arms via oil pressure, and are uncoupled via separate return springs when insufficient oil pressure is present. U.S. Pat. No. 8,251,032 is incorporated herein by reference as if fully set forth.
Arrangements are also known for a switchable finger follower in which the outer arm forms the primary lever, and the inner arm with the roller forms the secondary lever. These a locking device on the outer lever is normally engaged with the inner lever during normal valve operation. The valve is deactivated by disengaging the locking device from the inner lever so that the inner lever travels with a lost motion stroke against a return spring force when contacted by the cam, allowing the associated gas exchange valve to remain inactive.
It would be desirable to provide a finger follower of the type noted above with simpler manufacturing and reduced costs, as well as the possibility for additional valve lift positions.